The trains are the Stadler KISS model, from Switzerland.[1] Many in use worldwide since 2012. Caltrain is using the 25KV version, which is high for a commuter line but compatible with the California high speed rail system. (BART is 1KV. Streetcars are 400-600V.)
Some of the Caltrain electric trainsets are currently running, intermixed with the two generations of Diesel trains. And the occasional freight train, which is a Union Pacific operation.
I did see one electric trainset being towed by the breakdown locomotive, an old Diesel that Caltrain uses to recover stuck trains.